High octane number gasoline and method of manufacture



Jan. 14, 1936. 0, COTTRELL 2,028,1 21

HIGH OCTANE NUMBER GASOLINE AND METHOD OF MANUFACTURE Filed May 13, 1932Fig 1.

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Patented Jan. 14, 1936 HIGH OCTANE NUMBER GASOLINE AND v METHOD OFMANUFACTURE Osceola P. Cottrell, Scarsdale, N. 'Y., assignor to EdeleanuGesellschaft of Germany m. b. 11., a corporation Application May 13,1932, Serial No. 611,217

5 Claims. (01. 196-50) This invention relates to the manufacture of amotor fuel characterized by an especially high anti-knocking quality andconsequent high 'octane number.

More specific-ally, it relates to a process which combines steps ofcracking and treating with selective solvents, such as liquid-S02, orothers, such as are known in the'industry, in suchmannet that a givenamount of low boiling hydropurposes of illustration,

Fig. 1 is a flow diagram showing a multi-stage system of treatment; and

Fig. 2 is a flow diagram showing a recycling system of treatment.

Referring to Fig. 1, a cracking stock is cracked so as to form a crackedgasoline. Any method of cracking, liquid phase or vapor phase, at anytemperature and pressure may be used.

The cracked gasoline is then separated into a low boiling fraction and ahigh boiling fraction.

, This may be done by distillation of the condensed gasoline, or may be.accomplished directly by taking the higher boiling fraction oil theusual bubble tower of the cracking apparatus as a liquid side stream,while the lower boiling fraction is taken from the top of the bubbletower as a vapor, and subsequently condensed. The cut may be made at anypoint, depending on the type of stock and the desired quality of thefinished high octane number gasoline product, and is not restricted toany special temperature or gravity. 1

The high boiling fraction is then treated with a selective solvent, suchas liquid-S02, or mixed solvent, in the well known manner. The liquid-S02, or like solvent, dissolves out the unsaturated and aromaticconstituents and these are known as the extract, which is characterizedby having a high octane number. The remainder, comprising substantiallythe saturated constituents, is known as the rafiinate, and being knockproducing is characterized by having a low octane number. Both portionswill contain some of the solvent and this is removed by evaporation inthe usual manner.

The extract from the high boiling fraction is subjected to a suitablefinishing treatment for the removal of impurities-such as sulfurcompounds, gums, etc.,--and is blended with the low boiling fractionwhich has been similarly finished. The blend is a finished high octanenumber gasoline, and constitutes a very high quality of motor fuel. As amodification of this method, the low boiling fraction and the extractmay be first-blended and then finished to produce the high octane numberproduct.

Thus far the process is the same asthat de- 15 scribed in the patent toEdeleanu, No. 1,661,566, upon which it is an improvement. The presentprocess, however, provides for converting the entire stock into highoctane number motor fuel, that is, the raflinate from the high boilingfraction heretofore considered unsuitable for motor fuel because of itshigh boiling point and its knocking characteristic is also convertedinto a I high octane number gasoline suitable for motor fuel. This isaccomplished according to the fol- 25 lowing method.

The rafiinate from the treatment with liquid- S02 or like solvent,applied to the high boiling fraction of the cracked gasoline issubjected to a cracking operation. This is readily and economicallyeffected since the raflinate is comprised substantially of saturatedhydrocarbons. The product, a cracked gasoline, is then subjected to thesame process steps as was the original cracked gasoline stock. It isseparated into a low boiling fraction and a high boiling fraction. Thehigh boiling fraction is treated with liquid- $02 or the like, and theextract, after freeing from solvent and finishing, is blended with thefinished low boiling extract to form a finished high octane numbergasoline suitable for use as a high quality motor fuel. .The raifinateis treated in the same manner as the rafiinate from the originaltreatment, and so on over and over, until all of the original raifinatehas-been converted into high octane number gasoline. v

The foregoing method illustrates my invention in its simplest form. Inactual practice, however, instead of confining the successive stages oftreatment to the successive rafiinats, each successive raiiinate wouldbe mixed with a cracking stock and the admixture sotreated. This methadis shown in Fig. 1, by including the step of adding cracking stockrepresented by the dotted flow line. An'advantage of this procedure issults in a cracked low sulfur gasoline.

Example -A Midcontinent cracked gasoline was separated by distillationinto two portions, a fraction boiling below 347 F., and a higher boilingfraction. The yield of the low boiling fraction was 64.0% and that ofthe higher boiling fraction was 35.2% (distillation loss amounting to0.8%). The high boiling fraction was treated with liquid- S02, resultingin an extract yield of 42% and a raifinate yield of 58%. The extract wasfinished and blended with the low boiling fraction which was firstfinished. The blend resulted in a 'finished gasoline having a greatlyimproved distillation range and a 45% increase in octane number over theoriginal cracked gasoline. The end point of the finished gasoline thusmanufactured was 444 F. and its octane number was 83.

The rafiinate, representing over 20% of the original cracked gasoline,was mixed with cracking stock and recracked together with such stock,and the resulting cracked'gasoline was subjected to the same series ofsteps as was the original cracked gasoline; and this procedure wasrepeated with each successive raffinate.

In this manner substantially all of the original cracked gasoline wasconverted into finished high octane number gasoline, whereas if myimproved method had not been used, over 20% of the orig- -inal stock-thefirst rafiinatecould have been yield. The present invention resultsin afinished gasoline of such a favorable composition and distillation rangethat the end point may be considerably increased without adverselyaifecting its volatility in the motor or octane number.

Previously it was necessary to produce cracked gasoline having an endpoint of 390-400 F. to obtain a desired octane number which by thepresent method is obtained from a 437 F. or higher, end point gasoline.

Fig. 2 shows a continuous recycling method for carrying out myinvention. This process results in substantially all of a'crackedgasoline being converted into a high octane number gasoline, and all ofthe cracking stock employed is mixed with raffinate, so that crackingconditions are superior in .all cracking operations.

As in the first described method, the cracking stock is cracked intogasoline which is then separated into a low-boiling fraction and a highboiling fraction. The high boiling fraction is treated withliquid-SOg,or like solvent, and the extract blended with the low boiling fractionto produce the high octane number gasoline.

The distinguishing feature of this form of my invention is that therafiinate is led back and introduced into the original cracking stockenter.- ing the cracking step of the process. Thus the rafiinate iscontinuously recycled and a given portion is therefore graduallyconverted substan tially in its entirety into high-octane numbergasoline as a result of the successive crackings,

fractionations and selective solvent treatments.

to which it is subjected.

Fig. 2 also illustrates how the same principle may be used-forconverting either a cracked gasoline or a straight run gasoline intohigh octane number gasoline. In this case the raflinate is crackedand'the resulting cracked raftinate mixed with the cracked gasoline orstraight run gasoline entering the cycle (as shown by broken-line b'inFig. 2), the mixture then being separated into a low boiling fractionand a high boiling fraction which are disposed of in the manner alreadydescribed. No cracking stock is made use of, although, if desired,cracking stock may be simultaneously converted into high octane numbergasoline by mixing it with the rafiinate'to be cracked, as is evidentfrom Fig. 2 and the foregoing description.

It will be apparent to those skilled in the art that my invention may beapplied in many other ways. For example, in practically all crackingprocesses a recycle stock is obtained, being generally drawn off fromthe bottom of the bubble 'tower of the cracking plant. This recyclestock, containing such high boiling hydrocarbons as are not normallyusable, is led back and recracked with raw cracking stock in order thatit may be broken up into lower boiling hydrocarbons. As shown in Fig. 2,this procedure may be combined with the foregoing embodiments ofmyinvention as follows: Instead of mixing the raifinate directly withnew cracking stock and cracking the admixture, the raffinate is mixedwith the recycle stock from the cracking plant (indicated by broken linea in Fig. 2) and this admixture is mixed with new raw cracking stock andthe combined mixture subjected to cracking. The cracked gasoline productis then subjected to the same process steps already described.

My invention obviously is not restricted to the embodiments thereofillustrated and described,

but what I claim is as follows:

1. A continuous process for converting sub-' stantially all of astraight run gasoline into high octane number gasoline, comprising thesteps of separating the gasoline into a low boiling fraction and a highboiling fraction, treating the high boiling fraction .with liquid-S02 orlike solvent, separating the raflinate and extract, removing the solventtherefrom, cracking the rafiinate, re-

, cycling the cracked raflinate by mixing it with the straight rungasoline stock entering the cycle and blending said extract with saidlow boiling fraction to produce the high octane number' gasoline.

2. A process for the manufacture of high octane number gasolinecomprising mixing the liq- Hid-S02 insoluble hydrocarbons from the highboiling portion of a straight run gasoline with cracking stockcontaining both saturated and unsaturated hydrocarbons, cracking themixture to form a cracked gasoline, dividing the latter 2,oae,121

boiling fraction with liquid-S02 or like solvent,

separating the raflinate and extract, removing the solvent therefrom,blending said extract with said low boiling fraction to form a highoctane number gasoline, mixing said raflinate with cracking-stockcontaining both saturated and unsaturated hydrocarbons, cracking themixture so as to form a cracked gasoline, subjecting the latter to theforegoing sequence of steps described for the straight run gasoline, andin like manner treating the successive rafiinates resulting fromcontinuing the process herein set forth.

4. A continuous process for converting substantially' all of a straightrun gasoline into high octane number gasoline, comprising the steps ofseparating the gasoline into a low boiling fraction and a high boilingfraction, treating the high boiling fraction with liquid-SO: or likesolvent, separating the raffinate and extract, removing an the solventtherefrom, mixing the rafiinate with cracking stock and cracking themixture to form a cracked gasoline, mixing the latter with straight rungasoline entering the cycle, and blending said extract with said lowboiling fractionto produce the high octane number gasoline.

5. A continuous process for converting substantially all of a straightrun gasoline into high octane number gasoline, comprising the steps ofseparating the gasoline into a low boiling fraction and a high boilingfraction, treating the high boiling fraction with liquid-S02 or likesolvent, separating the raflinate and extract, removing the solventstherefrom, cracking the raflinate in admixture with recycle stock fromthe cracking step to form a cracked gasoline, mixing the latter withstraight run gasoline entering the cycle, and blending said extract withsaid low boiling fraction to produce the high octane number gasoline.

OSCEOLA P. CO'I'I'RELL.

